View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Springer - Publisher Connector Appl Petrochem Res (2014) 4:167–179 DOI 10.1007/s13203-013-0029-7 ORIGINAL ARTICLE Environmental impacts of ethylene production from diverse feedstocks and energy sources Madhav Ghanta • Darryl Fahey • Bala Subramaniam Received: 26 March 2013 / Accepted: 19 June 2013 / Published online: 23 July 2013 Ó The Author(s) 2013. This article is published with open access at Springerlink.com Abstract Quantitative cradle-to-gate environmental shows that for ethylene production, fuel burning at the impacts for ethylene production from naphtha (petroleum power plant to produce energy is by far the dominant crude), ethane (natural gas) and ethanol (corn-based) are source (78–93 % depending on the fuel source) of adverse predicted using GaBiÒ software. A comparison reveals that environmental impacts. the majority of the predicted environmental impacts for these feedstocks fall within the same order of magnitude. Keywords Ethylene Á Environmental impact analysis Á Soil and water pollution associated with corn-based eth- Fossil fuels Á Corn ethanol Á Life-cycle assessment ylene are however much higher. The main causative factor for greenhouse gas emissions, acidification and air pollu- tion is the burning of fossil-based fuel for agricultural Introduction operations, production of fertilizers and pesticides needed for cultivation (in the case of ethanol), ocean-based trans- Ethylene, with a worldwide consumption of 133 million portation (for naphtha) and the chemical processing steps tonnes/year, is the chemical industry’s primary building (for all feedstocks). An assessment of the environmental block [1]. Major industrial uses of ethylene include impacts of different energy sources (coal, natural gas and (a) polymerization to polyethylene and other copolymers; fuel oil) reveals almost similar carbon footprints for all the (b) oligomerization to normal alpha-olefins; (c) oxidation to fossil fuels used to produce a given quantity of energy. For ethylene oxide and acetaldehyde; (d) halogenation and de- most of the environmental impact categories, the GaBiÒ hydrohalogenation to vinyl chloride; (e) alkylation of ben- software reliably predicts the qualitative trends. The pre- zene to ethylbenzene; and (f) hydroformylation to dicted emissions agree well with the actual emissions data propionaldehyde [1–3]. In the USA, 70 % of the total eth- reported by a coal-based power plant (Lawrence Energy ylene production capacity comes from steam cracking of Center, Lawrence, KS) and a natural gas-based power plant naphtha and the remaining 30 % from the thermal cracking (Astoria Generating Station, Queens, NY) to the United of ethane [4]. The increased availability of natural gas (and States Environmental Protection Agency. The analysis thus ethane) in the USA, as a result of hydraulic fracturing of shale rock, has stimulated feasibility studies of building Electronic supplementary material The online version of this new ethylene crackers by Chevron Phillips Chemical article (doi:10.1007/s13203-013-0029-7) contains supplementary Company (1.5 million tonnes/year), LyondellBasell Indus- material, which is available to authorized users. tries (400,000 tonnes/year), Dow Chemical Company (900,000 tonnes/year), Shell Chemical Company (1 million M. Ghanta Á D. Fahey Á B. Subramaniam Center for Environmentally Beneficial Catalysis, University tonnes/year) and Sasol (1 million tonnes/year) [5, 6]. of Kansas, Lawrence, KS 66045-7609, USA An alternative source for ethylene is the dehydration of ethanol obtained from a renewable source, such as corn, & M. Ghanta Á B. Subramaniam ( ) sugarcane, and from cellulose or agricultural waste. Eth- Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS 66045-7609, USA ylene sourced from sugarcane is claimed to be greener than e-mail: [email protected] that produced from fossil fuel-based sources [7]. There is 123 168 Appl Petrochem Res (2014) 4:167–179 significant interest in green polyethylene from major procedures generally adopted to ultimately develop ISO- companies such as Procter & Gamble (consumer goods compliant reports. Hence, the conclusions are unaltered by manufacturer), Tetra Pak (packaging company) and these deviations. Shiseido (cosmetic company) [7]. Dow Chemical Com- A USA-specific environmental assessment is performed pany and Braskem have announced plans to construct an by employing the US-specific life-cycle inventory (USLCI) integrated complex for the production of polyethylene and an embedded software tool known as tools for reduc- based on sugarcane ethanol in Brazil [8]. While there is tion and assessment of chemicals and other environmental strong consumer interest in producing green polyethylene impacts (TRACI) [10, 13]. The TRACI software, devel- from biomass, the increased availability in the USA of oped by the United States Environmental Protection relatively inexpensive ethane feedstock has significantly Agency (USEPA), is designed based on the midpoint eroded the cost competitiveness of ethylene sourced from centric approach proposed by Intergovernmental Panel on renewable feedstocks. However, in the longer term, bio- Climate Change (IPCC). The TRACI methodology enables based feedstocks are the only sustainable option for pro- the generation of impact parameters that are USA specific. ducing chemicals. Empirical models developed by the US National Acid The cracking of naphtha or of ethane to ethylene is Precipitation Assessment Program and California Air highly energy intensive [9]. For ethylene production from Resource Board were utilized to estimate the acidification corn via ethanol, the ethanol concentration in the effluent and smog formation potential. Human health cancer and stream of the fermentation reactor dictates the energy non-cancer impact categories were estimated based on intensity for ethanol enrichment and its subsequent dehy- models developed using the USEPA Risk Assessment dration to ethylene. Further, the type of fuel used for Guidance and USEPA’s exposure factor handbook [14]. energy production influences the overall environmental The potential effects of various production operations on impact. In this work, we perform a comparative environ- environmental impact categories such as acidification, mental impact assessment (cradle-to-gate life-cycle analy- greenhouse gas emissions, ecotoxicity, human carcinogenic sis) to quantify the major contributors to the environmental and non-carcinogenic effects, and eutrophication are esti- impacts for ethylene production from naphtha, ethane and mated (see definitions in Supplementary Materials, ethanol, employing natural gas as the energy source in each Appendix A) [15]. case. In addition, we also compare the environmental impacts when using other fossil fuels such as coal and oil Basis of estimations and common assumptions as the energy sources. Where possible, we have also compared the GaBiÒ software predictions with reported The production basis for the estimated environmental plant emissions data in an attempt to establish the reli- impacts is assumed as 400,000 tonnes of ethylene/year ability of such predictions. from each of the following sources: naphtha (petroleum crude), ethane (natural gas) and ethanol derived from corn (biomass). We chose this basis to facilitate comparison of Methodology the GaBiÒ-predicted emissions/impacts with those reported by the ExxonMobil Baytown ethylene cracker with a Simulation similar production capacity. It should be clear that even though we do not use a functional unit of 1-kg ethylene GaBi 4.4Ò software [10] is employed to perform compar- produced (as per ISO guidelines), our quantitative results ative gate-to-gate, cradle-to-gate, and cradle-to-grave life- may be suitably scaled to obtain environmental impacts for cycle assessments (LCA) for ethylene and energy produc- a functional unit of 1-kg ethylene produced. For each tion. The raw material and energy datasets provided by source, a proportional allocation method based on the GaBiÒ are based on current technologies. The process energy content of the various products formed is employed simulation used in the GaBiÒ datasets incorporates process to estimate the environmental impacts of ethylene pro- (heat, water and mass) integration and waste treatment duction [10, 13]. We further assume that the electricity technologies. Even though the GaBiÒ software is designed requirement for all the feedstocks is met with natural gas as to perform environmental assessments and generate reports fuel (later in this manuscript, we also assess the environ- that conform to ISO 14040 [11] and ISO 14044 standards mental impacts of using other fossil-based fuels). [12], the current analysis deviates from those rigorous Although the current US electricity generation capaci- standards in certain areas such as the definition of a func- ties are similar for coal and natural gas [16], the majority tional unit, use of average market mix for representing (approximately 80 %) of the newer electricity generation diverse energy sources and the use of allocation. However, capacity in the US uses natural gas [17]. Hence, natural gas the environmental assessment methodology follows the is considered as the fuel source in this analysis. Given that 123 Appl Petrochem Res (2014) 4:167–179 169 valuable co-products are formed during the production of incorporates the environmental impacts of producing the ethylene, the absolute environmental